Energy efficiency has become an important factor in electric transportation machines. A particularly good technique for improving overall efficiency in this field is regeneration. Regeneration may involve converting kinetic energy of a vehicle (such as a car, truck, bus or watercraft) into stored electrical energy. In many instances, an electric motor converts electrical energy into kinetic motion, and the same motor, when operated as a regenerator, converts kinetic energy back into electrical energy. The electric energy typically is stored for example, in a capacitor bank, battery, or flywheel, for later re-use.
A good example of a motor/generator that alternately powers a vehicle and regenerates electricity is the Electric Wheel™, commercialized by Solomon Technologies Inc. of Tarpon Springs, Fla. As described for example in U.S. Pat. No. 5,863,288 entitled “Method and apparatus for propelling a marine vessel,” U.S. Pat. No. 5,851,162 entitled “System and apparatus for a multiple input and dual output electric differential motor transmission device,” and U.S. Pat. No. 5,575,730 entitled “Multiple-input infinite-speed integral motor and transmission device,” an embodiment of David Tether's invention operates by, among other things, combining mechanical energy with electric energy obtained through a permanent magnet motor. This technique is useful for a variety of applications. For example, the Toyota Prius, a popular hybrid automobile has adopted a ring gear system that, for a time combines the mechanical system used by the Electric Wheel with the output of a motor for propelling a car and regenerates energy during braking.
Regeneration, as described in the Solomon Technologies' patents and as followed by automakers such as Toyota, likely will become more dominant in the transportation industry. This technique often is used under a variety of motor conditions such as motor speed and loading. However, the motor/generator efficiency generally changes with operating condition. Accordingly, any method or device that compensates or mitigates the mismatch can lead directly to efficiency improvements. Another problem is that, while regeneration for land vehicles such as golf carts, cars and buses has been well implemented, regeneration for watercraft is in contrast much less developed. Accordingly, any tool that provides regeneration for watercraft should be a boon to this industry.